Engineers have been using magnesium alloys produced by adding various elements to magnesium for components such as packages of mobile devices including cellular phones and notebook personal computers and parts of automobiles. However, magnesium alloy, which has a hexagonal crystalline structure (a hexagonal close-packed structure), has poor plastic formability at ordinary temperature. Consequently, the magnesium alloy product used for the above-described packages and the like is mainly produced by using a cast material formed by the die casting process or thixomold process.
On the other hand, a malleable magnesium alloy such as AZ31, which is relatively easy to perform plastic forming, has been subjected to plastic forming such as press forming or forging. For example, engineers have been developing a press-formed body that is formed by performing press forming on a rolled sheet which is formed by rolling an ingot at a temperature range of 200° C. or more (under a warm condition or a hot condition), in the temperature range of which the prismatic plane and pyramidal plane of the hexagonal crystal develop slip deformation. To improve the plastic formability, engineers have studied the texture control of the magnesium alloy into a fine recrystallized texture by, for example, annealing the rolled sheet before the plastic forming (see Patent Literature 1). In addition, Patent Literature 2 has disclosed a technique of inclining the (0002) plane toward the rolled surface by subjecting the rolled sheet to a plurality of times of the treatment that combines a roller lever treatment and a recrystallization heat treatment. Patent Literature 2 intends to improve the plastic formability at 100° C. or below through this technique.    Patent Literature 1: the published Japanese patent application Tokukai 2007-98470    Patent Literature 2: the published Japanese patent application Tokukai 2005-298885